Figure



Se t. 24, 1963 .1. o. MELTON ETAL 3,104,364

AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS Filed March 22, 1961 7Sheets-Sheet 1 INVENTORS JamesdMeZialz h I & from M Car raider BY mw,wgm,p

ATTORNEYS Sept. 24, 1963 J. o. MELTON ETAL ,8

. AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS Filed March 22, 1961 7Sheets-Sheet 2 PO-S/T/VE' ACT/01V REZA y HmeAz/uc plesssues GOVEAA/OEINVENTORS James QMeZZozz [7'vi2z M. farperzfer ATTORNEYS Sept. 24, 1963J. o. MELTON .ETAL ,8

AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS 7 Sheets-Sheet 5 FiledMarch 22, 1961 g aw N.

Mm Ms W: whim um kuSQ Sept. 24, 1963 J. o. MELTYON ETAL 3,104;864

AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS Filed March 22, 1961 '7Sheets-Sheet 4 INVENTORS P 1963 J. o. MELTON ETAL 3,104,864

AUTOMATICCONTROL DEVICE FOR DRILLING APPARATUS Filed March 22, 1961' 7Sheets-Sheet 5 HUJIMI'IMJ' 67 7/ 89 9/ 70 f i 95 4: 2:;

@ l y. L5: 28 James 0 Malian [ruin /l Car van is?" BY I g g g g;MM3M,ML{M

TTORNEYS Sept; 24, 1963 J. o. MELTON ETAL 3,104,364

AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS Filed March 22, 1961 7Sheets-Sheet 6 4L VE' .S'UPPL Y INVENTORS y coA/r/eou E0 James 0. Malianour [ram M. Carpenter A ORNEYS Sept. 24, 1963 J. o. MELTQN Em 3,104,864

AUTOMATIC CONTROL DEVICE FOR DRILLING APPARATUS 7 Sheets-Sheet 7 FiledMarch 22, 1961 A I an Inn"? Mn 0 3 MM 0a C M ma J w 0 P ATTORNEYS UnitedStates Patent 3,104,864 AUTOMATIC CGNTROL DEVHIE FQR DRELLING APPARATUSJames 0. Melton, Norman, and Irvin M. Carpenter, Gklah-oma City, Okla,assignors to The Geolograph Company, ()lslahoma City, Okla, acorporation of Oklahoma Filed Mar. 22, 1961, er. No. 97,604 7 Claims.(Cl. 254173) The present invention relates to an apparatus capable ofuse in connection with a drilling rig and more particularly the presentinvention relates to certain improvements in an apparatus capable ofcontrolling, in an automatic manner, the weight exerted against thedrill bit of a rotary drilling rig, as will hereinafter appear indetail.

The present invention is an improvement over the invention disclosed andclaimed in copending application Serial No. 802,968, filed on March 30,1959, for Control Device For Drilling Apparatus.

The rate of drilling, or the rate of penetration of the drill bit intothe ground, will depend primarily upon the hardness of the earth layerwhich the bit engages; this drilling rate, within certain limits, willalso depend upon the load or weight applied to the bit, which in turndepends upon the rate at which the drill string is lowered. Logicallyenough, it has been ascertained that the feed or lowering rate of thedrill string should be correlated with the penetration rate of the drillbit in order to achieve optimum drilling; it has appeared further thatthe simplest method of effecting this correlation is by measuring andcontrolling the weight on the drill bit. Therefore, in present daypractice, the operator of a conventional drilling rig attempts to sensethe weight changes on the bit and, accordingly, feeds off suificientamount of drilling line in order to maintain a substantially constantweight on the bit. The operator accomplishes this result by firstwatching a weight indicator which is attached to the dead line at thedrilling rig; then, as the weight increases beyond a predeterminedvalue, the operator releases a braking means associated with thedrilling line so as to feed off the proper amount of additional line. asdistinguished from the inventions disclosed and claimed in the presentapplication and the aforementioned copending application.

The invention disclosed in the aforementioned copending applicationrelates to an apparatus of the type described above, and including thoseelements described above, wherein there is provided a feed control meanswhich is completely automatic. Such a system includes (a) a sensingdevice which bears against the dead line of the drilling rig and whichtransmits a pressure proportional to the tension in the dead line; (b) acontrol unit which is connected to the sensing unit and which provides apneumatic pressure output responsive and proportional to the pressuretransmitted from the sensing device; (c) an air motor connected to thebraking mechanism and to the control device for the purpose of releasingand engaging the braking mechanism in response to the pressure at thesensing device; (d) a governor having a friction wheel bearing againstthe cable drum and operating a valve to deenergize the air motor whenthe drilling speed becomes excessive; and (e) a plurality of This latterprocedure is, of course, entirely manual,

Patented Sept. 24, 1963 intermediate elements adapted to eliminate anyag in response and, at the same time, to provide safety features in thecontrol system itself.

In comparing the present invention with that of the aforementionedcopending application, the following main improvements are featured inthe present invention:

(1) In the basic system of the prior copending application, the controlpoint :of the governor is manually adjustable; in the present inventionthis adjustment is made pneumatically and, further, is remotelycontrolled.

(2) In the prior basic system, it has been discovered that the pressurebetween the controller and the air motor tends to build up, especiallyduring very slow drilling; the present invention provides anintermittent bleed-oft to prevent this build-up.

(2) In the prior basic system, it has been discovered that there areoccasional lags and sticking of valves such that the air motor is notalways immediately deenergized when the output pressure decreases fromthe controller; the present invention provides an additional safetyvalve operating directly from the controller to deenergize the air motorimmediately, and much faster than heretofore attainable, when the outputpressure from the controller decreases.

(4) The cont-roller of the present invention has been modified tocontrol the valve referred to in paragraph (3) a new feature of thisinvention involves the employment of a spring-loaded pivot pin for theflapper, as will hereinafter appear.

Therefore, it is a principal object of the present inven tion to providean improved system for maintaining the weight on the drill bitsubstantially constant.

It is another important object of the present invention to provide anautomatic control system of the type referred to above wherein theelements constituting the control system may be simply attached, oradded, to a conventional drilling rig without requiring any furthermodifications or changes in the structure of the drilling rig itself.

It is a further object of the present invention to provide an automaticcontrol system of the type referred to above wherein the brake controlmeans is made completely responsive to the change in the tension in thedead line and wherein response lags are minimized or eliminatedentirely.

it is a further object of the present invention to provide an automaticcontrol system of the type referred to above wherein safety means areincluded to cause engagement of the brake when the tension in the deadline exceeds a certain predetermined value due to the passage of thedrill :bit into a gas pocket, or due to a break-oil, or other similarcondition.

It is a further object of the present invention to provide a system ofthe type referred to above wherein the control point of the governor isremotely controlled.

It is a further object of the present invention to provide a bleed-oilvalve, and operating means therefor, for preventing the pressure frombuilding up between the controller and the air motor, especially duringslow drilling.

It is a further object of the present invention to provide a safetyvalve which results in a more rapid and more positive deenergization ofthe air motor when the tension in the dead line decreases.

It is a still further object of the present invention to provide aspring-loaded pivot pin for the flapper in the controller.

Other and further objects and advantageous features of the presentinvention will hereinafter more fully appear in connection with adetailed description of the drawings which:

FIGURE 1 is a view in elevation, partly diagrammatic, showing aconventional drilling rig employing the novel control system of thepresent invention;

FIGURE 2 is a pneumatic circuit diagram corresponding to the elementsillustrated in FIGURE 1;

FEGURE 3 is a sectional view, on an enlarged scale, of the airmotor andits associated quick-release valve and safety Valve shown in FIGURE 1;

FIGURE 4 is a fragmentary side elevation, partly in section, showing thegovernor employed in the present invention;

FIGURE 5 is a front elevation, on an enlarged scale, showing the detailsof some of the internal components of the controller illustrated inFIGURES l and 2;

FIGURE 6 is a sectional view, on an enlarged scale, taken along sectionline 66 of FIGURE 5, showing details of the spring-loaded pivot pin;

FIGURE 7 is a sectional view, on an enlarged scale, taken along sectionline 77 of FIGURE 5, showing details of the flapper, the nozzle and theinternal valve, the latter operating the safety valve; and

FIGURE 8 is a sectional view, on an enlarged scale, of the pneumaticrelay shown in FIGURE 2.

Referring to the drawings in detail, FIGURE 1 shows a conventionalderrick 1 supporting at its upper end a crown block 2, the latterincluding two or more conventional pulleys. A cable 3, secured at oneend 4 to the frame of the derrick passes around one pulley 5 of thecrown block 2, then downwardly and around a pulley 6 in a movable ortravelling block 9. From the travelling block the cable 3 passesupwardly and around a second pulley 5 of the crown block. The cable 3may then pass downwardly to a winding drum 10. As many pulleys (orsheaves) 5 and 6 are included in the crown block and travelling blockrespectively, to provide the number of lines required to support theload.

The portion of the cable 3 extending from the anchor 4 to the crownblock 2 is referred to as the dead line. The portion of the cable 8extending from the crown block down to the winding drum 10 is referredto as the fast line. Any conventional winding means including a motor,gears, clutches, etc. (which form no part of the present invention) maybe employed for the purpose of driving the winding drum 10.

Traveling block 9 is connected to the kelly 12 through a swivel head 13,the kelly 12 extending through a rotary turntable 14; the drill string(not shown) is secured to the lower end of the kelly 12. and carries atits lower end a suitable lbit (not shown) for drilling through thevarious earth formations.

Adjacent the one end of winding drum 10 there is shown,diagrammatically, a braking mechanism consisting of a brake arm 15pivotally mounted on a support 16- and a brake band 17 which 'bearsagainst a brake drum 11 secured to one end of the winding drum 10. Atthe righthand end of the brake arm 15 there is a spring 18 which is ofsufiicient size to urge the brake band 17 against the brake drum 11 soas to prevent the winding drum 10 from rotating. If desired, the spring18 could be replaced by a weight (not shown) of suitable size.

The above described apparatus is essentially conventional and admits ofmanual operation as is; i.e., the operator can lift up on the right-handof the brake arm 15 so as to release the brake whenever he feels that itis desirable to increase the weight on the drill bit. The elements whichconstitute the automatic control system of the present invention, andwhich will be described hereinafter, may now be added to the abovedescribed conventional apparatus without requiring, any further changesor modifications of the existing rig structure. Conversely, afterattachment, the elements of the instant automatic control system may besimply removed, or otherwise disabled, and the rig may be operatedmanually in the prior conventional manner.

In accordance with the present invention, there is provided aweight-sensing mechanism consisting of a hy-.

draulic sensing unit 21 which has a sensing plunger 22 urged against thedead line 3. This sensing unit II also includes a pair of cable guides23 and 24 through which the cable 3 is permitted to pass. Preferably,one of these cable guides is firmly secured to the cable/the otherallowing the cable to slide freely therethrough. Thus, the

sensing plunger 22 contacts the portion of the cable 3' between the twocable guides 23 and 24. A suitable hydraulic fluid is introduced throughthe sensing device 21 through a suitable fitting (not shown) which isclosed when the sensing system is filled to the desired level.

A conduit 28 connects with the sensing device 21 and transmits the fluidpressure therein to a control means,

diagrammatically indicated by the reference numeral .29

port 35 adjacent the brake arm 15. In the simplified.

form of the invention shown in FIGURE 1, the air motor is connected tothe output, or controlled pressure, line 33 of the controller 29 througha quick release valve 36, also known per se, Also, as shown in FIGURE 1,the air motor 34 has an arm 33 actuated by the motor and a cable 39extending from one end of the arm 38 around a pulley li to one end ofthe brake arm 15 and adjacent the spring 18.

The pulley 40 is mounted on an overhead support 41 which is attached tothe upper end of the support 35.

Also shown in FIGURE 1 are the friction wheel of the governor (later tobe described) bearing against the flange of the brake drum 11, a safetyvalve 200, a check valve 171 and a recording unit generally designatedby the reference character 300.

FIGURE 2. shows a pneumatic circuit which is designed for completelyautomatic operation. The various elements, some of which are describedin greater detail hereinafter, will be described in connection with thecom- 'bination shown in FIGURE 2 as follows:

The air supply which is available at any conventional rig passes intothe system through the inlet conduit and to the air scrubber 151. Fromthe air scrubber 15-1, the pressurized air passes through a manualcut-ofi valve 153 and through a pressure regulator-filter 152, which isessentially of conventional design and will not be further described ingreater detail. From the pressure regulator 152, the air supply passesthrough the conduit 30 connect ing with the controller 29 (later to bedescribed in detail). The conduit 1 36 leading to the air clamp 135 alsoconnects with the pressure regulator 152 as shown. Thus, when the systemis turned on, pressure is supplied to the air clamp 135 irrespective ofwhat happens to the elements shown at the right in this figure.

The outlet conduit 3-3 from the controller connects with a positiveaction relay having an outlet conduit 161. The positive action relay isa standard purchased item, known per se, which will not be furtherdescribed except briefly as follows: The output pressure delivered bythe positive action relay from its outlet conduit 16-1, will be equalto, or proportional to, the pressure coming pressure within theconduit33 rises above a predetermined level (for which a suitablesetting has been provided internally of the positive action relay), therelay will be tripped internally such that the output pressure at theconduit 161 will be reduced to zero. In other words, this positiveaction relay is a pneumatic safety device to stop the action of thedriller in case of a twist-01f or when drilling into a cavity.

The outlet conduit 161 of relay 160 feeds air under controlled pressureto the pneumatic relay 225, later to be described in detail. Briefly,however, the pneumatic relay 225 supplies air at its outlet conduit 231at a pressure equal to that supplied from the conduit 161 and, hence,from the controller 29. The pneumatic relay 235 is connected to thepressure regulator 152 by means of a conduit 235. The pressure suppliedby the pneumatic relay 225 (as will more clearly appear hereinafter), isequal to the output from the controller 29 but does not draw airdirectly from the output of the controller. The outlet conduit 231 ofthe pneumatic relay 235 feeds air under controlled pressure to theone-to-one relay 162 through conduit 163.

The one-to-one relay 162 is known per se and it functions to produce aresult similar to that of the pneumatic relay 225. This relay 162 isconnected with the high pressure source of air through valve 165,conduit 164 and pressure regulator 154, the latter being connected inparallel with the pressure regulator 152. The outlet conduit 166 of therelay 162 connects with the quick release valve 36. The action of therelay 162 is such that, when there is pressure in the conduit 163, therelay will permit air to pass from the conduit 164 into the outletconduit 166 at a pressure equal to that in the conduit 163 and for thepurpose of operating the air motor 34. The quick release valve 36connects with the air motor 34 through the T connection 64.

The outlet conduit 231 of the pneumatic relay 225 also connects withanother con-duit 170 leading to a check valve v17-1 which opens only inthe direction of the arrow in FIGURE 2. The check valve :171 connectswith a bleed-0T1 valve 237 through conduit 238. The bleed-ofl? valve,described below, connects with the governor casing 102 by means of aconduit 121 as will appear hereinafter. Conduit 1'21 connects with aninternal valve in the governor which vents the air pressure in theconduit 121 to the atmosphere when the speed of the cable drum exceeds apredetermined value. Thus, this decrease in pressure will serve todeenergize the air motor 34.

In connection with slow speed drilling, it has been observed that thepressure on the outlet side of the controller 2-9 tends to build up, forreasons that are not entirely understood. Therefore, the bleed-off valve237 intermittently opens to the atmosphere to bleed off the excesspressure in the conduits 121 and 238. The bleed-oft" valve 237 isprovided with an actuating arm 239 which, in the position shown inFIGURE 2, provides direct communication between the conduits 12-1 and238. The outer end of the arm 239 is provided with a roller 240 whichengages the teeth of the sprocket wheel 241, the latter being mountedfor rotation on the shaft 242 above the bleed-01f valve 237. As thesprocket wheel 241 turns, the various teeth thereon will engage theroller 241) so as to pivot the arm 239 intermittently and in acounterclockwise direction from that shown in FIGURE 2. In thecounterclockwise position of the arm 239, the bleed-01f valve 237 willbleed oil? the excess pressure in the conduits 121 and 238 to theatmosphere. Shaft 242 can be connected to rotate in response to anycontinuously moving device including, for example, the rotary turntableor to a device which operates in response to the rate of drilling. Byway of example, FIGURE 1 shows the conduits 121 and 238 leading to arecording device 309 which has therein a main shaft (not shown) movablein response to the rate of drilling. The shaft 242 can be appropriatelydriven by the main shaft referred to above.

A pneumatic means (described in detail hereinafter), is

mounted within the governor 102 for the purpose of varying the controlpoint of the governor. This pneumatic means is connected by means ofconduit 143 to another pressure regulator 155 which is connected inparallel with pressure regulators 1'52 and 154. Adjustment of thecontrol on the pressure regulator 155 will determine the control pointat which the governor 102 will operate.

As will hereinafter appear, a safety valve 200 connects with the airmotor 34 through the T connection 64. This safety valve also connectswith the controller 29 by means of the conduit 201. As will hereinafterappear, this safety valve operates in response to a decrease in inputpressure from the conduit 28 below a predetermined value to deenergizethe air motor immediately. The hydraulic pressure in the conduit 28 isdirectly proportional to the tension in the dead line 3 and is providedby the hydraulic sensing unit 21. A detailed description of theoperation of the entire combination shown in FIGURE 2 will appearhereinafter following the specific disclosure of certain of theelements.

The air motor 34, quick release valve 36 and the safety valve 200, allreferred to above, are shown in further detail in FIGURE 3 and will bebriefly described as follows:

The air motor 34, which is essentially of a conventional design,comprises a spring loaded plunger 45 which is pivotally attached at itsouter end to the arm 33. The

arm 38 is pivotally attached at its lower end to a bracket 46 mounted onthe base 47 of the air motor. The air motor also includes an air-tightcasing 48 and a bellowstype diaphragm 49, the latter being secured atone end to the inner end of the spring loaded plunger 45. Ringstiifeners 55 are provided to hold the folds of the diaphragm in properposition during expansion and contraction of the diaphragm. A helicalspring 51 is located internally of the diaphragm 49 for the purpose ofurging the diaphragm and the plunger to the left. The casing 43 isprovided with an external opening 52 at which a suitable fitting islocated. A threaded horizontal rod 53 is also secured to the right-handportion of the casing 48 for the purpose of providing limits for thepivotal movement of the arm 38. For this last-mentioned purpose, thereare provided nuts 54 and 55 and washers 56 and 57.

The quick release valve 36 includes a plurality of ports 60, 61, 62 and63. The port 60 is plugged; the port 61 is connected with theatmosphere; the port 62 is connected to the opening 52 of the casing 48of the air motor 34 by means of a T connection 64; the remaining port 63is connected to the source of controlled air pressure by means of aconnection 65. The internal portion of the quick release valve 36includes a flexible and springloaded diaphragm 66 which is shown in itsnormal condition of repose in FIGURE '3. The diaphragm 66 has theability to provide controlled air pressure from the line 166 through theport 62 to the air motor 34 when the controlled air pressure is soprovided through the. conduit 33. However, when the air pressure in theconduit 33 falls below the pressure previously supplied to the air motor34, the diaphragm 66 in the quick release valve 36 will move so that theair within the air motor will be permitted to pass backwardly throughthe quick release valve through the port 61 to the atmosphere. Thus,when the air pressure within the conduit 33 falls below a certain value,the air motor 34 is immediately cut off due to the venting action ofthhe quick releasevalve 36. In the absence of the quick release valve36, there would be a certain amount of lag in the operation of the airmotor 34. The safety valve 200 operates briefly as follows: when thecontroller 29 is operating in response to a hydraulic pressure above apredetermined value from the dead line sensing unit 21, an internalvalve in the controller will (in a manner later to be described) directthe full pressure from the regulated air supply to the safety valve 200through the conduit 201. The safety valve is provided with three ports202, 203 and 204; port 202 communicates with the conduit 201; port 203communicates with the port 52 of the air motor 34 through the Tconnection 64. A diaphragm 2&5 is mounted in the cavity 2% of the safetyvalve 200 in such a manner as to close ofi (internally) port 2&3 whenthe pressure in conduit 291 is equal to the full value of the regulatedsupply. However, when the pressure falls below this value, the diaphragm2115 will move downwardly, venting the pressure in the port 253 to theatmosphere, and at the same time, deenergizing the air motor 34. Whenthe hydraulic pressure from the dead line falls below a predeterminedvalue, the internal valve 95 in the controller will cut oif the supplyof air to the conduit 201 and, at the same time, will bleed the pressurein this conduit to the atmosphere.

FIGURE 4 shows a governor or safety device employed for the purpose ofpreventing the drill string from being lowered too fast, as for example,when the drill bit should pass into a gas pocket or the like. Thegovernor includes a friction wheel keyed to a shaft 101. The frictionwheel 1% is adapted to bear against the outer peripheral flange of thewinding drum 1% (as shown in FIGURES 1, 2 and 4). The casing 162 of thegovernor also includes a concentrically mounted shaft 1% which is drivenby the shaft 191 through suitable gearing inside the casing 102. Thegearing is considered as essentially conventional and, hence, is notshown. A cross bar 1% is secured to the shaft 1193 for rotationtherewith. A pair of fly weights, generally designated by the referencecharacter 105, are pivotally mounted (as at 1%) adjacent the oppositeends of the cross bar 11%. Each fly weight 195 has an inner arm 1&7adapted to bear against a flange 1118 of a slidable sleeve 199. At theright-hand end of the casing 102, as it appears in FIGURE 4, a slidablepiston 11% is mounted in a cylindrical opening 111.

At the right-hand end of the casing 102, a hollow tubular member 112threadedly engages a threaded portion 113 of the governor. A shortcylindrical member 114 having therein a recess 117 abuts against theright-hand end of the tubular member 112 in such a manner that therecess is in alignment with the bore of the tube. A rotatable coupling118 is received on the short cylindrical member114 and threadedlyengages the right-hand end of the tubular member 112 so as to secure thecylindrical member 114 against it. The piston 110 is provided with anextension in the form of a rod 11$ which projects into the bore of thetube of 112. A cup 125 is mounted on the end of the rod 119 as shown. Ahelical spring 133 surrounds the right-hand end of the rod 119 so as tobear against the right-hand end of the threaded portion 113 and thebottom of the cup 125. A flexible diaphragm 134,

being cup-shaped in its normal condition of repose is mounted within thecavity (formed by the bore of the tube and the recess 117) in such amanner that its folded edge 141 is received in a suitably shaped recess142 formed in the mating portions of the tube 112 and the cylinder 114.A conduit 143, which is connected to the source of air pressure in amanner not shown on this figure, threadedly engages a hole in thecylinder 114 and communicates with the recess 117 through theright-angled passageway 144. The left-hand end of the slidable piston110 is provided with a disc 115. A ball 116 is received within suitablyopposed and aligned cavities on the adjacent portions of the disc 115and the slidable sleeve 1119 as shown.

The upper right-hand put of the housing 162 includes a valve portion121} to which is connected a conduit 121 containing air under pressure(from a source lat-er to be described). The valve portion 120 alsoincludes a slidable valve stem 122 which is urged towards the left underthe action of the spring 123 so as to hold the conical portion 124- ofthe valve in its corresponding seat.

The pressure of the air in the conduit 14-3 can be varied from thesource as desired and this pressure is transmitted to the flexiblediaphragm 134 which bears against the cup 125 urging the same toward theleft against the action of the spring 133. As will appear below, thevalue of the pressure from the conduit 143 will determine the A ultimaterotary speed of the winding drum necessary to move the piston 11%towards the right such that the valve 125 will be opened.

It the winding drum 1% were now rotating rapidly, its

If the force transmitted from the slidable sleeve 189 through the ball116, piston 111i and rod 119 to the cup 125 is sufiicient to overcomethe force exerted onthe cup by the membrane 134 (resulting from thepressure of air from the line 143), then the sleeve 1119 and the piston11%) will be moved to the right. The disc would then bear against thevalve stem 122, moving the conical portion 124 away from its seat so asto Vent the pressure in the conduit 121 to the atmosphere through theopening 126. As indicated above, the controlled pressure from theconduit 14-3 will determine the maximum speed required of the windingdrum to open the valve I 129; since the conduit 121 connects with thesupply of air to the air motor, the opening of the valve will serve todeenergize the air motor so as to cause engagement of the brake.

Casing 152 is pivotally mounted, as at 127, on a pair of verticalstandards 12 3 (only one of which is shown in FTGURE 4).

connects with a lug 131 at the lower right-hand portion of the casingN12 and also with a lug 132 on the base 129 so as to urge the casing 162in a pivotal direction (with respect to the standards 12$) tending toforce the friction wheel 1th) out of contact with the peripheral flangeon the winding drum 1%.

An air clamp 135 is mounted on the base 129 for the purpose of urgingthe casing 1% in a pivotal direction opposite to that effected by thespring so as to bring the friction wheel 10% into contact with theperipheral flange of the winding drum 1%. This air clamp is connected toa primary source of pressure through a conduit 136. A vertically movableplunger 137 is mounted withina' central cylindrical chamber 138 in theair clamp 135. A a

short rod 139, connected at its lower end to the center of the plunger137, projects outwardly through an appropriate holein the air clamp 135.A small vent 149 is also provided in the upper portion of the clamp andleading to the central chamber 138.

When a source of air under pressure is supplied to the conduit 136 andto the central chamber 138, the plunger 137 and the rod 139 will bemoved vertically upwards. The rod 139, contacting the lower right-handportion of the casing 1112, will pivot the casing 192 in acounterclockwise direction, about the pivotal points 127, so as to urgethe friction wheel 1 into engagement with the peripheral flange on thewinding drum 11 This last described condition represents the operatingposition ofthe governor shown in FIGURE 4. The base 129 with itsappropriate supporting structure is mounted in a position adjacent thewinding drum so that the friction wheel 109 can be caused to bearagainst a peripheral flange of the winding drum 1% in the mannerdescribed above.

FIGURES 5, 6 and 7 show the operation of the controller 29. Air underpressure is supplied from the normal source of :air pressure at the rigto the controller 29 through the conduit 31} appearing in FIGURE 5. Thehydraulic pressure which effects the control within the controller 29 isconducted to the controller from the diaphragm on deadline through theconduit 28 appearing The vertical standards 12% are secured at theirlower ends to a base support 129. Aspring 130' action of the controllerwill be briefly described as follows:

The Bourdon tube 71] moves in accordance with the fluctuation ofhydraulic pressure in the conduit 23 so as to move the flapper 72 aboutthe pivot 71 relative to the nozzle 73.

The nozzle 73 is suitably threaded into a nozzle block 74 which, inturn, is connected to the air supply from the conduit 3%) through thepressure indicator 75 and conduit 76. As best shown in FIGURE 7, thenozzle 73 is threadedly received in the hole 7 9 in the nozzle block 74.The nozzle block 74 is also provided with two ports 80 and 81communicating with the hole 79. The port 8i} communicates with theconduit 76 which supplies air to the nozzle, whereas the port 81communicates with the conduit 78 which conducts the air under controlledpressure away from the nozzle. The nozzle 73 is provided with aninternal bore 82 in which is received a plug 83. The plug 83 is providedwith a restricted orifice 84 and the nozzle itself is provided with arestricted orifice 85. The portion of the nozzle 73, in the region ofthe port 81, is provided with a plurality of holes 36. The plug 83 ispositioned,

in such a manner that, when the flapper 72 moves away from the nozzle73, a venturi eifect is created within the nozzle so as to draw a slightsuction on the conduit 78, thereby providing a more rapid response.

The action of the flapper 72 against the nozzle 73 will now be describedin relation to both FIGURES and 7: when the pressure in the Bourdon tube7a is at a maximum, the flapper 72 will be moved to its closest positionrelative to the nozzle 73 and, if desired, even to the extent of closingoff the orifice 35; under such a condition, the air passing into thehole 79 of the nozzle block 74 (through the conduit 76 and the port 80)will pass through the orifice $4 of the plug 33, through the holes 86and outwardly into the conduit 78 through the port 31. Under the latterconditions, the pressure in the conduit 78 will ultimately reach thepressure in the conduit 76. As the pressure in the Bourdon tubedecreases, however, the flapper 72 will be moved progressively fartheraway from the nozzle 73 so that an increasing quantity of air will issueforth from the nozzle 73 through the orifice 85. Thus, the pressure inthe conduit 78 will be reduced below the pressure in the conduit 76 byan amount commensurate with the sizes of the orifices 34 and 85 and inaccordance with the distance between the flapper 72. and the nozzle 73.

The nozzle block 74 is mounted on a sub-frame 87 which is pivotallyconnected to the frame 88 of thecontroller 29 by means of the nut 99,the latter permitting pivotal movement of the subfirame 87 so as to varythe initial position of the flapper 72 relative to the nozzle 73. Thispivotal movement of the subframe 87 can be effected by means of thetoggle 89 which is pivotally attached adjacent the upper portion of thesubframe 8 7, the threaded rod 91 which is attached to the toggle 89,the lug 92 which is attached to the frame 88 of the recorder 29 and thetwo nuts 93 and 94 which are received on the threaded rod 91 on oppositesides of the lug 92.

The air under controlled pressure from the nozzle block 74 passes fromthe conduit 73 through the pressure indicator 77 and to the conduit 33marked Controlled Air Out (inFIGURE 5 As indicated heretofore, thecontroller 79 is provided with an internal valve 95 which is employedfor operating the safety valve 230. As best shown in FIGURE 7, thisinternal valve. 95 comprises a threaded fitting 96 which is received ina suitable threaded opening 97 in a block 98. The block 98 is mounted onthe subframe 87 opposite from the block 74.

The block 98 is also provided with two ports 2% and 299 communicatingwith the threaded hole 97 and connecting with conduits 2G1 and 99respectively. Conduit 201 connects with the safety valve 290, asdescribed heretofore, and conduit 99 connects with the conduit 30through the pressure indicator 75'.

Mounted within the fitting 96 is a pin 210 which is moveable axially ofthe fitting. The pin 2.10 is provided with a central enlarged portion211 having convex surfaces on its left-hand and right-hand ends. Theinternal bore 207 of the fitting 96 is provided with a guide 212 and aninsert 213 forming a seat for the right-hand end of the enlarged portion211. The left-hand end of the bore 207 is provided with a concavesurface 215 which constitutes a seat for the left-hand end of theenlarged portion 211.

In the position shown in FIGURE 7, the air supply will pass through theconduit 99, into the hole 97 in the block 98, through the openings inthe guide 212, and the insert 213, through the holes 214, and throughthe conduit 201 to the safety valve 200; under these conditions, thepressure beneath the diaphragm 205, as it appears in FIGURE 3, would besubstantially the full value of the regulated supply entering throughthe conduit 99. With the left-hand end of the member 211 being seated onthe surface 215, no air will leak between the pin 210 and the holethrough which the pin passes. However, when the pin 210 is moved to theright, there will be suflicient clearance between the parts to permitair to seep between the pin and the hole in the fitting 96 in which thepin is received.

Now, if the pressure from the dead line falls below a predeterminedvalue, the Bourdon tube 70 will move in such a way as to pivot theflapper 72 about the pivot pin 71 so that the lower end of the flapper73 will come into contact with the pin 210 to move the latter axiallytoward the right. At this point, the valve portion 211 will seat againstthe member 213 shutting off the supply of air from the conduit 99 to theconduit 201. At the same time, the 'air which seeps between the pin 210and the hole in the fitting 96 in which the pin is received, Will reducethe pressure in the line 291 immediately so that the safety valve 200will per'ate, instantaneously to deenergize the air motor 34.

Assuming that the pressure in the Bourdon tube 70 was suflicien-tly lowthat the pin 210 would be moved to its extreme right-hand position, ifthe pressure in the Bourdon tube were lowered still further, there wouldbe a tendency for the flapper 72 to bend or for the pivot pin 71 tobend. Hence, the structure shown in FIGURE 6 is provided to prevent abending or breaking of the flapper 72 or to prevent a breaking orbending of the pivot pin were it not otherwise mounted. The pivot pin71, shown in FIGURE 6, is'received in an elongated hole 216 in the block217. A helical spring 213 having its ends engaging the left-hand end ofthe pin and the central portion of the block 217 continuously urges thepivot pin 71 towards the right as it appears in FIGURE 6. The subframe87 is provided with an elongated vertical slot 219'. The block 217 isprovided with a corresponding rearwardly projecting portion 229. Theprojection 22% is adapted to fit into the vertical slot 219. A threadedbolt 221 passes through a suitable hole in the projection 220. By meansof the not 222 and washer 223, the block 217 can be adjusted to anyvertical position as provided by the movement of the projection 220within the slot 219.

FIGURE 8 shows the details of a pneumatic relay 225. The port 22 6connects with the positive action relay 162 through the conduit 161, thepositive action relay itself being connected to the output of thecontroller 29 in a manner described heretofore. As the pressure from thecontroller increases, air enters the port 226 and acts upon thediaphragm 227 forcing the central shaft 228 toward the right; thismovement of the central shaft 228 will cause the inlet valve 229 to openpermitting air from the supply to pass into the central chamber 230 fromthe conduit 23-6. Air from the central chamber will then pass into theconduit 23-1 through port 2 32. Conduit 231 connects with the relay 162and the check valve 171 as indicated heretofore. The inlet valve 229will remain open until the pressure in the conduit 231 is equal to 11the pressure in the conduit 162. When these two forces become equal, thediaphragm 227 and the shaft 228 will return to their normal positions;closing the inlet valve 229. However, if the pressure in the conduit ratdecreases thereafter, the pressure in the conduit 231 and in the centralchamber 236 will act upon the diaphragm 227 forcing the shaft 228towards the left so as to open the bleed valve 233, thus allowing theair in the conduit 231 to bleed to the atmosphere. The bleed valve willremain open until the pressures in conduits 161 and 231 become equal.When these two forces become equal, the diaphragm 227 and the shaft 228will return to their normal positions, closing the bleed valve 253. Anadditional diaphragm 234- is provided to support the other end of theshaft 228. An equalizing orifice 235 is provided to equalize thepressure on the opposite sides of the diaphragm 234. The purpose of therelay 225 is to supply air to the air motor ultimately at a pressureequal to the output pressure from the controller 2? Without, at the sametime, drawing air directly from the output of the controller.

Operation (1) Referring now to all of the drawings, and in particular toFIGURE 2, it will be assumed that a drilling operation is taking place.It will be assumed'further, that the weight on the drilling bit asreflected by the tension in the dead line 3 is within the minimum andmaximum limits of operation. The controller will have its elementsapproximately in the positions shown in FIG- URE 5. The governor willhave its elements in the positions shown in FIGURE 4. The brake will beconsidered as engaged as represented by the relative positions of theelements shown in FIGURE 3.

(2) From the assumed conditions above, let it now be assumed that thedrilling has progressed to the extent that the tension in the dead line3 has exceeded the maximum predetermined value for the operation of thepresent invention. Under this latter condition, pressure in the conduit28 will increase, causing the Bourdon tube 70 to expand so as to movethe flapper '72 closer to thenozzle 7d. Movement of the flapper 72towards the nozzle 73 will decrease the quantity of air coming from theorifice 85 and, in turn, will raise the value of the pressure in theconduit 78 towards the pressure in the conduit 7 6. The increasedpressure in the conduit 78 will reflect a similar increase in pressurein the conduits 33, 161, 231, 163 and 166 to the quick release valve 36,opening the same and energizing the air motor so as to lift the arm ofthe brake and, thus, permitting the drill string 12 to descend. Thedrill string will descend until the pressure in the dead line 3 isreduced to a value which will cause a reverse operation of the variouselements described and in such a manner as to reengage the brake means.Under normal operating conditions, the brake will be released andreengaged intermittently so as to produce a substantially constanttension in the dead line 3 within the minimum and maximum limitsreferred to above.

(3) From the conditions described above in paragraph (;1), let us nowassume that the drill bit has passed into an air pocket such that itbegins to descend at a rapid rate and in such a manner that the tensionin the dead line increases to a maximum. The following control andsafety deatures will come into operation:

'(a) The speed of the winding drum 10, being excessive, will cause thefly weights 105 to be thrown centrifugally outward opening the valve 124and reducing the pressure in the air motor so as to reengage the brake;

(b) The flapper 72 will have closed off fully the nozzle 35 in theorifice 73. The output pressure in the conduit 33 from the controller 2%will be at a maximum and this maximum will be above the limit set in thepositive-action relay 16%. Thus, the positive-action relay will reducethe pressure in the lines between it and the air motor substantially toatmospheric pressure. ensure that the brake will be reengaged.

(4) It will be assumed that the drill string is descending and that thetension in the line '3 suddenly decreases by a large amount. The Bourdontube 70' will be contracted to such an extent that the flapper 72 willcontact the pin 21% moving the latter towards the right (as it appearsin FIGURE 7). Under the latter condition, the air supply from theconduit 99 will be shut off; the pressure in the conduit Zlll will bereduced and the safety valve 2% will open so as to deenergize the airmotor 34 and to engage the brake. Not only will the operation of thesafety valve 209, in the manner described herein,

assist in the deenergizing of the air motor 34- when the pressure in thedead line decreases extremely rapidly, but also, this safety valve 209,by itself, will serve to deenergize the air motor in the event that oneor more of' the valves between controller 29 and the air motor 34 shouldotherwise become inoperative. Furthermore, if the pressure in theBourdon tube 70 should become extremely low, the pivot pin '71 would beurged toward the left against the action of the spring 218 so as toprevent possible damage to the flapper '72 or to the pivot pin itself.

(5) Under conditions of extremely slow drilling, it has been observedthat the pressure in the conduits leading from the controller 29 to theair motor 34- tends to build up for reasons that remain somewhatobscure. As

indicated heretofore, the sprocket wheel 241 will be rotated by theshaft 242 so as to operate the bleed-off valve 267 so as to prevent thebuild-up of pressure in conduits 121 and 238 (6) If for any reason, itis desired to change the control point of the governor 102 so as toreflect a ditferent maximum speed of the cable drum 10, the outputpressure in the conduit 143 from the pressure regulator can be increasedor reduced by adjusting the external control on the pressure regulator155. This change in pressure in the conduit 143 will like-wise produce achange in pressure within the recess 1 17', the change in pressure inthe recess 117 will, of course, be reflected by a change in forceexerted by the diaphragm 134 against the right-hand end of the cup 125.Thus, it will appear that the control of the governor 162 can beeffected hydraulically and remotely.

Although it has been stated above that the pressure on the outlet sideof the controller 29' tends to build-up for reasons that are notentirely undersood, or for reasons that remain somewhat obscure, it isbelieved that this pressure build-up is due, in part at least, tofrictional effects in the various adjusting points and pivots in thecontroller and in various valves and other moveable members, and totemperature effects as well.

Whereas the present invention has been described in particular relationto the drawings attached. hereto, it should be understood that other andfurther modifications, apart from those shown or suggested herein, mightbe made within the spirit and scope of this invention.

What is claimed is:

1. In a drilling rig including a frame, an upper pulley.

block secured to said frame, a lower movable pulley block, upper andlower pulleys rotatably mounted within said pulley blocks, respectively,a drill string supported from said lower block, a rotatable cable drum,a cable wound against said cable drum so as to prevent rotation of thesame, the improvementwhich comprises an automatic control systemincluding a weight sensing device containingflhydraulic fluid thereinand having a sensing element bearing against said cable, said sensingelement being movable in response to the changes in tension in saidcable for producing in said sensing device a fluid pressure in saidhydraulic fluid proportional to the tension'in said This will alsoserveto cable, a fluid pressure responsive actuator attached to saidbrake means and adapted upon energization to release said brake means, acontroller connected between said sensing device and said actuator forincreasing the fluid pressure in said actuator for energizing saidactuator in response to an increase in fluid pressure in said sensingdevice and so as to release said brake when the tension in said cableexceeds a predetermined value, a quick release valve connected betweensaid controller and said actuator for venting the fluid pressure in saidactuator to the atmosphere so as to deenergize said actuator in responseto a decrease in output pressure from said controller, a safety valveconnected to said actuator, and means connected to said safety valve andresponsive to a decrease in pressure in the hydraulic fluid in saidsensing device for opening said safety valve to vent the pressure insaid actuator to the atmosphere to deenergize said actuator.

2. In a drilling rig including a frame, an upper pulley block secured tosaid frame, a lower movable pulley block, upper and lower pulleysrotatably mounted within said pulley blocks, respectively, a drillstring supported from said lower block, a rotatable cable drum, a cablewound on said cable drum passing around the pulleys of said pulleyblocks and secured at one end to said frame whereby the unwinding ofsaid cable drum will cause the drill string to descend, and a brakemeans normally hearing against said cable drum so as to prevent rotationthereof, the improvement which comprises an automatic control systemincluding a weight sensing device having a sensing element bearingagainst said cable adjacent the fixed end thereof, said sensing elementbeing movable in response to the changes in tension in said cable, apressure controller having an inlet connected to a primary source of airunder pressure and an outlet supplying air from said primary source at avariable pressure, a movable element mounted in said controller andadapted by its movement to effect said variable pressure at said outlet,means connecting said movable element of said controller with saidsensing device and forming a closed fluid circuit, said sensing element,when moving in response to changes in tension in said cable producing afluid pressure in said closed fluid circuit proportional to the tensionin said cable, said means connecting said sensing device with saidmovable element transmitting the change in fluid pressure caused by themovement of said sensing element to move said movable element inaccordance with the change in pressure in said closed fluid cirwit,- thepressure of air at the outlet of said valve thereby varying inaccordance with the changes in tension in said cable, an air motormounted adjacent said brake means and having thereon an arm movable inaccordance with pressure in said air motor, a brake cable connected fromone end of said arm to said brake means, a quick release valve, said airmotor having an inlet connected to the outlet of said controller throughsaid quick release valve, said air motor when the air pressure thereinincreases in accordance with the increase of air pressure thereto fromsaid controller through said quick release valve moving said arm so asto tension said brake cable and release said brake means, said quickrelease valve having therein means for venting the pressure within saidair motor to the atmosphere when the outlet air pressure from saidcontroller decreases, a safety valve connected to the inlet of said airmotor, and a pilot valve mounted in said controller and connecting withsaid safety valve, said pilot valve being actuated by said movableelement in response to a decrease in pressure in said closed fluidcircuit so as to open said safety valve to vent the pressure in said airmotor to the atmosphere thereby deenergizing said air motor.

3. In a drilling rig including a frame, an upper pulley block secured tosaid frame, a lower movable pulley block, upper and lower pulleysrotatably mounted within said pulley blocks, respectively, a drillstring supported from said lower block, a rotatable cable drum, a cablewound on said cable drum passing around the pulleys of said pulleyblocks and secured at one end to said frame whereby the unwinding ofsaid cable drum will cause the drill string to descend, and a brakemeans nonmally bearing against said cabledrurn so as to prevent rotationthereof; the improvement which comprises an automatic control systemincluding a weight sensing device having a sensing element bearingagainst said cable adjacent the fixed end thereof, said sensing elementbeing movable in response to the changes in tension in said cable; apressure controller having therein a nozzle valve and a pivotal flapper;said nozzle valve having an inlet connected to a primary source of airunder pressure, an orifice arranged in registry with said flapper, andan outlet supplying air from said primary source at a variable pressuredepending upon the movement of said flapper relative to said orifice; anexpansible element mounted in said con troller; means connecting saidexpansible element of said controller with said sensing device andforming a closed fluid circuit; said sensing element, when moving inresponse to changes in tension in said cable, producing a fluid pressurein said closed fluid circuit proportional to the tension in said cable;a pivot pin mounted in said controller, said flapper being connected atone end to said expansible element and being pivotal about said pivotpin such that the other end of said flapper is movable towards and awayfrom said orifice; said means connecting said sensing'device with saidexpansible element transmitting the change in fluid pressure caused bythe movement of said sensing element to said expansible element forpivoting said flapper relative to said orifice in accordance with thechange in pressure in said closed fluid circuit, the pressure of air atthe outlet of said valve thereby varying in accordance with the changesin tension in said cable; an air motor mounted adjacent said brake meansand having thereon an arm movable in accordance with pressure in saidair motor; a brake cable connected from one end of said arm to saidbrake means; a quick release valve; said air motor having an inletconnected to the outlet of said controller through said quick releasevalve; said air motor, when the air pressure therein increases inaccordance with the increase of air pressure thereto from saidcontroller through said quick release valve, moving said arm so as totension said brake cable and release said brake means; said quickrelease valve having therein means for venting the pressure within saidair motor to the atmosphere when the outlet air pressure from saidcontroller decreases; a safety valve connected to the inlet of said airmotor; and a pilot valve mounted in said controller and connecting withsaid safety valve, said pilot valve being actuated by said flapper inresponse to a decrease in pressure in said closed fluid circuit so as toopen said safety valve to vent the pressure in said air motor to theatmosphere thereby deenergizing said air motor.

4. Apparatus as set forth in claim 3 including means for mounting saidpivot pin slidably and resiliently relative to said controller.

5. In a drilling rig including a frame, an upper pulley block secured tosaid frame, a lower movable pulley block, upper and lower pulleysrotatably mounted within said pulley blocks, respectively, a drillstring supported from said lower block, a rotatable cable drum, a cablewound on said cable drum passing around the pulleys of said pulleyblocks and secured at one end to said framewhereby the unwinding of saidcable drum will cause the drill string to descend, and a brake meansnormally bearing against said cable drum so as to prevent rotationthereof, the improvement which comprises an automatic control systemincluding a weight sensing device having a sensing element bearingagainst said cable adjacent the fixed end thereof, said sensing elementbeing movable in response to the changes in tension in said cable, apressure controller having an inlet connected to a primary source of airunder pressure and'an outlet'supplying air from said primary source at avariable pressure, a movable element mounted in said controller andadapted by its movement to eifect said variable pressure at said outlet,means connecting said movable element of said controller with saidsensing device and forming a closed fluid circuit, said sensing element,when moving in response to changes in tension in said cable producing afluid pressure in said closed fluid circuit proportional to the tensionin said cable, said means connecting said sensing device with saidmovable element transmitting the change in fluid pressure caused by themovement of said sensing element to move said movable element inaccordance with the change in pressure in said closed fluid circuit, thepressure of air at the outlet of said valve thereby varying inaccordance with the changes in tension in said cable, an air motormounted adjacent said brake means and having thereon an arm movable inaccordance with pressure in said air motor, a brake cable connected fromone end of said arm to said brake means, a quick release valve, said airmotor having an inlet connected to the outlet of said controller throughsaid quick release valve, said air motor, when'the air pressure thereinincreases in accordance with the increase of air pressure suppliedthereto from said controller through said quick release valve movingsaid arm so as to tension said brake cable and release said brake means,said quick release valve having therein means for venting the pressurewithin said air motor to the atmosphere when said air pressure suppliedfrom said controller decreases, a governor mounted adjacent said cabledrum, a circumferential flange on said cable drum, a shaft mounted forrotation within said governor, a friction wheel mounted on first shaftand bearing against said circumferential flange, a slidable valveactuator mounted within said governor, means mounted within saidgovernor and movable in accordance with rotary speed of said shaft formoving said valve actuator in a given direction, a valve mounted in saidcasing of said governor and being opened by said valve actuator when thespeed of said shaft exceeds a predetermined value, a conduit connectingsaid valve in said governor to the output of said controller, whereby,when the unwinding speed of said winding drum exceeds a certain value,the output of said controller will be vented to atmosphere through thevalve in said governor, a bleed-off valve in said conduit, and means forintermittently opening said bleed-off valve.

6. In a drilling rig including a frame, an upper pulley block secured tosaid frame, a lower movable pulley block, upper and lower pulleysrotatably mounted within said pulley blocks, respectively, a drillstring supported from said lower block, a rotatable cable drum, a cablewound on said cable drum passing around the pulleys of said pulleyblocks and secured at one end to said frame whereby the unwinding ofsaid cable drum will cause the drill string to descend, and a brakemeans normally bearing against said cable drum so as to prevent rotationthereof, the improvement which comprises an automatic control systemincluding a weight sensing device having a sensing element bearingagainst said cable adjacent the fixed end thereof, said sensing elementbeing movable in response to the changes in tension in said cable, apressure controller having an inlet connected to a primary source of airunder pressure and an outlet supplying air from said primary source at avariable pressure, a movable element mounted in said controller andadapted by its movement to effect said variable pressure at said outlet,means connecting said movable element of said controller with saidsensing device and forming a closed fluid circuit, said sensing element,when moving in response to changes in tension in said cable producing afluid pressure in said closed flu id circuit proportional to the tensionin said cable, said means connecting said sensing device with saidmovable element transmitting the 1'6" 7 change in fluid pressure causedby the movement of said sensing element to move said movable element inaccordance with the change in pressure in said closed fluid circuit, thepressure of air at'the outlet of said valve thereby varying inaccordance with the changes in tension in said cable, air motor mountedadjacent said brake means and having thereon an arm movable inaccordance with pressure in said air motor, a brake cable connected fromone end of said arm to said brake means, a quick release valve, said airmotor having an inlet connected to the outlet of said controller throughsaid quick re lease valve, said air motor, when the air pressure thereinincreases in accordance with the increase of air pressure suppliedthereto from said controller through said quick release valve movingsaid arm so as to tension said brake cable and release said brake means,said quick release valve having therein means for venting the pressurewithin said air motor to the atmosphere when said air pressure suppliedfrom said controller decreases, a governor mounted adjacent said cabledrum,-a circumferential flange on said cable drum, a shaft mounted forrotation within said governor, a friction wheel mounted on said shaftand bearing against said circumferential flange, a slidable valveactuator mounted within said governor, means mounted within saidgovernor and movable in accordance with rotary speed of said shaft formoving said valve actuator in a given direction, a valve mounted in saidcasing of said governor and being opened by said valve actuator when thespeed of said shaft exceeds a predetermined value, a conduit connectingsaid valve in said governor to the output of said controller, whereby,when the unwinding speed of said winding drum exceeds a certain value,the output of said controller will be vented to atmosphere through thevalve in said governor, a bleedoff valve in said conduit, a pivotal armmounted on said bleed-off valve and operable to open said bleed-oilvalve to the atmosphere when said pivotal arm is pivoted in apredetermined direction, a roller mounted on one end of said pivotalarm, a sprocket shaft mounted above said pivotal'arm, means for rotatingsaid sprocket shaft, and

a sprocket wheel mounted on said sprocket and having thereon a pluralityof sprocket teeth engageable with said roller for pivoting said pivotalarm intermittently in said given direction so as to reduce the pressurein said conduit intermittently.

7. In a drilling rig including a frame, an upper pulley block secured tosaid frame, a lower movable pulley block, upper and lower pulleysrotatably mounted within said pulley blocks, respectively, a drillstring supported from said lower block, a rotatable cable drum, a cablewound on said cable drum passing around the pulleys of said pulleyblocks and secured at one end to said frame, whereby the unwinding ofsaid cable drum will cause the drill string to descend, and a brakemeans normally bearing against said cable drum so as to prevent rotation7 thereof, the improvement which comprises an automatic control systemincluding a weight sensing device having a sensing element bearingagainst said cable adjacent the fixed end thereof, said sensing elementbeing movable in response to the changes in tension in said cable, apres-- sure controller having therein an inlet connected to a primarysource of air under pressure and an outlet supplying air from saidprimary source at a variable pressure depending upon the movement ofsaid sensing element, the pressure of air at the outlet of saidcontroller thereby varying in accordance with the changes in tension insaid cable, an air motor mounted adjacent said brake means and havingthereon an arm movable in accordance with pressure in said air motor, abrake cable connected from one end of said arm to said brake means, saidair motor having an inlet connected to the outlet of said controller,

said air motor, when the air pressure therein increases in accordancewith the increase of air pressure supplied thereto from said controllermoving said arm so as to tension said brake cable and release said brakemeans,

1 7 a governor mounted adjacent said cable drum, a circumferentialflange on said cable drum, a shaft mounted for rotation Within saidgovernor, a friction wheel mounted on said shaft and engageable withsaid circumferential flange, a slida'ble valve actuator mounted Withinsaid governor, operating means mounted in said governor and movable inaccordance with the rotary speed of said shaft for moving said valveactuator in a given direction, a valve mounted in said governor andbeing opened by said valve actuator when the speed of said shaft exceedsa predetermined value, a conduit connecting said valve of said governorto the output of said controller, whereby, when the unwinding speed ofsaid ca'ble drum exceeds a certain value, the output of said controllerwill be vented to atmosphere through the valve in said governor,resilient means in said governor bearing against said operating meansand biasing the same for movement in said given direction, a pneumaticchamber mounted on said governor, means supplying fluid under pressureto said chamber, means for remotely varying the pressure of the fluidsupplied to said chamber, and a flexible diaphragm mounted in saidchamber bearing against said operating means for exerting a forcethereon in opposition to said resilient means.

No references cited.

1. IN A DRILLING RIG INCLUDING A FRAME, AN UPPER PULLEY BLOCK SECURED TOSAID FRAME, A LOWER MOVABLE PULLEY BLOCK, UPPER AND LOWER PULLEYSROTATABLY MOUNTED WITHIN SAID PULLEY BLOCKS, RESPECTIVELY, A DRILLSTRING SUPPORTED FROM SAID LOWER BLOCK, A ROTATABLE CABLE DRUM, A CABLEWOUND ON SAID CABLE DRUM PASSING AROUND SAID PULLEYS OF SAID PULLEYBLOCKS AND SECURED AT ONE END TO SAID FRAME WHEREBY THE UNWINDING OFSAID CABLE DRUM WILL CAUSE SAID DRILL STRING TO DESCEND, AND A BRAKEMEANS NORMALLY BEARING AGAINST SAID CABLE DRUM SO AS TO PREVENT ROTATIONOF THE SAME, THE IMPROVEMENT WHICH COMPRISES AN AUTOMATIC CONTROL SYSTEMINCLUDING A WEIGHT SENSING DEVICE CONTAINING HYDRAULIC FLUID THEREIN ANDHAVING A SENSING ELEMENT BEARING AGAINST SAID CABLE, SAID SENSINGELEMENT BEING MOVABLE IN RESPONSE TO THE CHANGES IN TENSION IN SAIDCABLE FOR PRODUCING IN SAID SENSING DEVICE A FLUID PRESSURE IN SAIDHYDRAULIC FLUID PROPORTIONAL TO THE TENSION IN SAID CABLE, A FLUIDPRESSURE RESPONSIVE ACTUATOR ATTACHED TO SAID BRAKE MEANS AND ADAPTEDUPON ENERGIZATION TO RELEASE SAID BRAKE MEANS, A CONTROLLER CONNECTEDBETWEEN SAID SENSING DEVICE AND SAID ACTUATOR FOR INCREASING THE FLUIDPRESSURE IN SAID ACTUATOR FOR ENERGIZING SAID ACTUATOR IN RESPONSE TO ANINCREASE IN FLUID PRESSURE IN SAID SENSING DEVICE AND SO AS TO RELEASESAID BRAKE WHEN THE TENSION IN SAID CABLE EXCEEDS A PREDETERMINED VALUE,A QUICK RELEASE VALVE CONNECTED BETWEEN SAID CONTROLLER AND SAIDACTUATOR FOR VENTING THE FLUID PRESSURE IN SAID ACTUATOR TO THEATMOSPHERE SO AS TO DEENERGIZE SAID ACTUATOR IN RESPONSE TO A DECREASEIN OUTPUT PRESSURE FROM SAID CONTROLLER, A SAFETY VALVE CONNECTED TOSAID ACTUATOR, AND MEANS CONNECTED TO SAID SAFETY VALVE AND RESPONSIVETO A DECREASE IN PRESSURE IN THE HYDRAULIC FLUID IN SAID SENSING DEVICEFOR OPENING SAID SAFETY VALVE TO VENT THE PRESSURE IN SAID ACTUATOR TOTHE ATMOSPHERE TO DEENERGIZE SAID ACTUATOR.